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1.
排沙漏斗的水沙分离性能取决于其流场特性,为了弄清楚悬板开孔对流场特性的影响,利用粒子图像测速技术和数值模拟方法,分别对悬板溢流段和非溢流段同时均匀布孔、仅在非溢流段布孔和无孔时的排沙漏斗流场特性开展研究。结果表明：①布孔位置不影响涡流性质但影响其强度,均匀布孔时涡流强度最小,不利于水沙离心分离;②无孔和仅在非溢流段布孔时的流场特性有利于泥沙径向输移、沉降和排出,均匀布孔径向速度和二次流流速减小不利于泥沙输移和排出;③仅在悬板非溢流段布孔时悬板表面速度大于其他方案,泥沙不易淤积于悬板。为减少悬板上的泥沙淤积量且同时要保证较高的泥沙截除率时可采用仅在悬板非溢流段布孔的方案优化悬板体型。 相似文献
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排沙漏斗的水沙分离性能取决于其流场特性,为了弄清楚悬板开孔对流场特性的影响,利用粒子图像测速技术和数值模拟方法,分别对悬板溢流段和非溢流段同时均匀布孔、仅在非溢流段布孔和无孔时的排沙漏斗流场特性开展研究。结果表明:①布孔位置不影响涡流性质但影响其强度,均匀布孔时涡流强度最小,不利于水沙离心分离;②无孔和仅在非溢流段布孔时的流场特性有利于泥沙径向输移、沉降和排出,均匀布孔径向速度和二次流流速减小不利于泥沙输移和排出;③仅在悬板非溢流段布孔时悬板表面速度大于其他方案,泥沙不易淤积于悬板。为减少悬板上的泥沙淤积量且同时要保证较高的泥沙截除率时可采用仅在悬板非溢流段布孔的方案优化悬板体型。 相似文献
3.
A.J. Baer 《Precambrian Research》1977,5(3):249-260
The rate of thickening of the lithosphere has varied through geological time. Plate tectonics did not begin until about 1000 Ma ago, because eclogite was not stable in oceanic crust prior to that time. Geological data (presence of continental margins and rift-zones, paleomagnetic polar-wander curve, age and distribution of andesites) are used as a guide to extrapolate back in time the data available on the present lithosphere and on present geothermal gradients. These speculations are meant to focus attention on constraints that must be respected by models for Precambrian evolution of the crust. 相似文献
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Results of the ecostratigraphic analysis using statistical data handling of radiolarian fauna from the sections of holes 434, 434A, 434B firstly allow us: 1) to identify the stratigraphic succession and some hiatuses in the hemipelagic sedimentation, 2) to determine the age of basal layers of the sedimentary cover as an Oligocene-Early Miocene boundary. These results present a new data on the age and environmental conditions of the formation of the sedimentary cover on the landward slope of the Japanese Trench. The “layers with radiolarians” correspond to previously established areas. The boundaries of “layers with radiolarians” marked by radiometric dates obtained on sections of the Japan Sea on transect: holes 436, 439 and 584. These results revealed the periodicity of the sedimentation process. 相似文献
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pH值对长石溶解度及次生孔隙发育的影响 总被引：19，自引：0，他引：19
本文从长石溶解反应的机理及各离子形态在溶液中分布的热力学角度出发 ,论述了pH值对三个长石端员及高岭石在流体中溶解度的影响。在此基础上 ,进一步探讨了流体酸碱度对长石向高岭石转化和次生孔隙发育程度的制约 ,并提出了衡量次生孔隙发育程度的参数———转化系数D。 相似文献
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Numerous studies on the potential of hydrocarbon generation by the rocks of the sedimentary cover of the northern Precaspian Basin are based either on the interpolation of measurements from a relatively sparse boreholes network or on the numerical estimations of the history of development of the hydrocarbon potential under the assumption of a steady temperature gradient both with depth in the sedimentary cover and with time during basin evolution. By the example of sedimentary sections from the northeastern part of the Precaspian Basin, variations in thermal history and petroleum formation conditions were numerically analyzed for the rocks underlying the salt complex of the basin. Variations in the temperature gradient and thermal properties of the rocks with depth and time were accounted for in the modeling. Numerical reconstructions of the thermal and maturation history of sedimentary sections from the basin were used to estimate the influence of evaporite sequences on the thermal history, the maturation level of organic matter, and the hydrocarbon generation potential of the subsalt complex of the basin. The calculations showed that this influence could be significant, but there remained an uncertainty related to the absence of reliable data on the time and rate of salt diapir formation. 相似文献
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岩石圈内能变化导致岩石的形成和消亡。组成岩石圈的三种不同类型岩石的形成和消亡过程在岩石圈表面引起不同的大地构造效应。大洋岩石圈和大陆岩石圈的演化效应存在互补关系:前者内能升高导致岩石形成,反之岩石消亡;后者内能升高导致岩石消亡,反之岩石形成;前者造成平、剖面上均自洋中脊向外变老的岩石序列,后者造成平面上自陆核向外变新,剖面上自重熔界面向上和向下变新的岩石序列。 相似文献
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水岩作用对雅鲁藏布大拐弯北段滑坡的影响 总被引：12，自引：1，他引：12
通过对川藏公路南线八一至然乌段实地考察及对考察结果，已有资料的分析，本文运用统计学原理探讨了雅鲁藏布大拐弯北段地区滑坡与水岩作用的关系，并结合该地区发育的滑坡灾害具体分析了该地区水岩作用与滑坡的关系。经分析认为，该地区水岩作用条件复杂且利于发育各种典型的水岩作用，但地域性特殊的水岩作用形式更发育，并对雅鲁藏布地区滑坡灾害形成，诱发都有重要影响。 相似文献
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全新世环境考古研究进展 总被引：1，自引：1，他引：0
环境考古研究是国际上的热点问题之一,尤其是针对全新世以来的研究.以往的研究主要集中在气候突变事件对新石器文化的影响、人类对环境变迁的调整与适应、人类对于环境的影响与干预以及史前农业与气候环境的相关等方面.研究结果表明:极端气候事件的确对人类文化与农业文明产生了深远影响,但是人类也一定程度上对气候变迁做出了调整与响应.尽管在很长时间内,人类处于被动角色,但是随着时间延续,人与自然间关系也发生重大变动,逐步演变为人类对于自然的强烈影响与干预.目前各国科学家对此两个问题的讨论已经逐步摆脱定性阶段,开始向定量化方向发展.孢粉、磁化率、有机质等代用指标的运用,使得这一领域具有了更为广阔的前景和生命力.史前农业的研究牵涉的内容较为复杂,包括农业起源、农业传播以及农业发展过程中的诸多问题,它们与气候以及人类活动的关系一直是环境考古学家努力探索的方向,至今该领域的研究仍然存在很大争论和分歧. 相似文献
11.
矿山地质灾害危险性评估中几个问题的商榷 总被引：2，自引：0，他引：2
笔者认为,为了合理、有效地开发利用矿产资源,在进行矿山地质灾害危险性评估过程中不要采用“禁采区”,建议采用围护带;在现行“规范”规定的基础上应根据各个矿山的具体情况可适当扩大围护带宽度,但不宜超过30m;在计算煤(矿)层顶板安全厚度的系数取值时,应考虑煤(矿)层倾角和围护等级;只有考虑了这些因素获得的地质灾害危险性评估结论,才具有适用性,才能真正为矿山设计和进行地质灾害防治工作提供科学依据。 相似文献
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A.O. Volynets M.M. Pevzner M.L. Tolstykh A.D. Babansky 《Russian Geology and Geophysics》2018,59(12):1577-1591
Based on the geochemical characteristics of the Miocene-Quaternary volcanic rocks of the Sredinny Range of Kamchatka, we divide it into northern and southern provinces; the latter comprises the “eastern”, “western”, and “central” flanks. We present new data on the composition of Neogene-Quaternary volcanic rocks in the southern part of the Sredinny Range of Kamchatka: Khangar and Icha volcanic massifs and Mt. Yurtinaya on the “western” flank, Bystrinsky and Kozyrevsky Ridges on the “eastern” flank, and Anaunsky Dol and Uksichan massif located in between. We show systematic differences in the composition of rocks from the “western” and “eastern” flanks. During the Neogene, a typical island-arc volcanism took place within the “eastern” flank. Quaternary volcanic rocks of this area have both island-arc and within-plate geochemical features. We propose to call rocks of this type hybrid rocks. Within the “western” flank, hybrid volcanism has been manifested since the Neogene, while typical island-arc rocks are not found. Magma generation processes on the “western” flank of the Sredinny Ridge are influenced by an enriched mantle source; the effect of fluid is less pronounced here as compared to the rocks of the “eastern” flank, where it is clearly traced. 相似文献
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居住在山区的人们主要活动空间是斜坡。人们对斜坡利用的有效与否是由人们对斜坡认识充分与否决定的。倘若人们对斜坡认识不足，就可能遭受因斜坡失稳所带来的损失。因此，对这类斜坡的稳定状况的正确认识很有必要。以清江流域典型滑坡——瓦屋场滑坡的复活为例，通过介绍清江流域瓦屋场滑坡人类活动与该滑坡产生的变形情况，根据滑坡体工程地质条件，针对变形原因用萨尔玛法及不平衡推力法进行了稳定分析，同时对复活机制进行分析。在此基础上按照顺应性准则和协调性原则，提出相应的工程治理措施。鉴于该滑坡为该地区的典型滑坡，从灾害学角度说明人类在利用坡体前，对坡体稳定状况认识的重要性并给出人们合理利用该地区自然边坡的建议。 相似文献
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黑河流域山前绿洲灌溉农田蒸散发模拟研究 总被引：13，自引：3，他引：10
基于Penman-Monteith蒸散公式, 应用土壤-植被-大气系统水分和能量传输理论对Shuttleworth-Wallace蒸散模型的参数进行改进, 得出解析计算农田作物蒸腾和土壤蒸发的双源模型. 对黑河流域山前绿洲农田春小麦生长期土壤蒸发、作物蒸腾以及总蒸散过程进行了模拟研究. 对模型的计算结果以田间观测和水量平衡方法进行验证, 误差目标NSE=0.98, 说明该模型用于农田蒸发和蒸腾的计算是合理的. 对影响蒸发和蒸腾的主导因子净辐射、叶面积指数、土壤含水量进行了相关性分析, 得出三者的变化对土壤蒸发、作物蒸腾的影响. 通过不同时期日蒸散发量变化特征的分析, 表明土壤、冠层两个界面对能量和水汽传输的交互影响效应显著. 相似文献
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《Geochimica et cosmochimica acta》1999,63(7-8):967-987
The conventional view of the climatic influence on weathering is that weathering rates are strongly temperature-dependent due to the near-exponential relationship (Clausius-Clapeyron) between temperature and the saturation vapor pressure of water, and hence precipitation and runoff. This is a central theme in the Earth “thermostat” model, i.e., weathering of aluminosilicate rocks on continents acts through the greenhouse effect as a negative feedback on atmospheric CO2. However, there is very little direct field evidence to support this hypothesis. To remedy the lack of systematic geochemical data for cold high latitude rivers as compared to the tropics, large, pristine drainages of Eastern Siberia have been studied. Here, data from basement terrains of the Siberian Craton are reported. The low Si to total cation ratios suggest a superficially weathered system. The total dissolved solids flux of 0.39 × 106 mol/km2/yr and the CO2 uptake flux of 149 × 103 mol/km2/yr are similar to those of the tropical cratonic systems and the collisional/accretionary zone of northeastern Siberia, but about a factor of 3 lower than for the orogenic zones of the western Americas at both low and high latitudes. The lack of systematic climatic effects on the solute and CO2 fluxes is ascribed to the unique non-glacial frost shattering processes which continuously expose fresh rock surfaces and, thus, overcome the effect of temperature inhibition on high-latitude shields and to the lateritic cover that seals in the weathering front away from the weathering agents on the tropical shields. No primary climatic effects on weathering rates on the present Earth were detected. 相似文献
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黄河河曲段冰塞水位的分析计算 总被引：2，自引：0，他引：2
本文根据黄河河曲段６年的实测资料，分析了该冰塞河段冰期水位的变化规律，讨论了该河段冰塞水位的变化与冰塞演变的相互关系。建立了冰塞水位变化的参数关系式，基于原型的观测研究，对试验室模拟冰塞的水位进行了分析研究，研究表明：试验室模拟冰塞水位的变化规律与天然河道中冰塞水位的变化规律相同。由此，可以进行冰塞水位的计算及其预报。 相似文献
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N. K. Andreeva N. A. Kagramanyan T. N. Kheraskova 《Lithology and Mineral Resources》2000,35(4):373-389
New data on the stratigraphy and composition of the Devonian rocks of the Moscow Syneclise were used. Facies-paleogeographic
schemes were compiled for the Lochkovian, Eifelian, Givetian, early-middle Frasnian, late Frasnian, and early-late Famennian
evolutionary stages of the Moscow Syneclise. Seven sedimentation cycles were developed due to sealevel fluctuations and structural
rearrangements in the paleooceanic basins surrounding the East European Platform at that time. The inference was made on the
structural heterogeneity of the platform basement and on differentiated movements as well as on the strike-slip fault nature
of some fragments of the basement relative to each other in the Devonian. 相似文献
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David A. Mendez Edelmira D. Gálvez Luis A. Cisternas 《International Journal of Mineral Processing》2009,90(1-4):1-15
The present study summarizes reports on optimal flotation circuits design over the period from 1989 to present. A review is made on the resolution characteristics of each study, leading to a classification of the approaches into four different groups, in which conclusions are based on either (A) mathematical solutions without binary variable, (B) mathematical solutions with binary variable, (C) heuristic solutions, or (D) genetic algorithms. These groups aim at a common scheme of resolution, varying in both flotation and milling models employed, characteristics of their superstructures, and functions which each study proposes to optimize, as well as the effects of the application of each strategy on the form of the solution of the circuit (selection of stages, selection of equipment, and dimensions of equipment).Within these either implicit or explicit multi-objective optimization problems there are challenges strongly related to the obtaining of better flotation and milling/classification models, as well as the treatment of uncertainty related to important parameters (kinetics, composition, external economic factors) and changes in previously established configurations using methods in which the designer's criteria influence the application of models and restrictions on the problem. Also, the incorporation of environmental issues needs more attention. 相似文献